Space invader fuse issue

[Paulf]

Hi, just got space invaders pin back from my brother. He said he'd switched it on that morning and only the lights came on, nothing else.
Brought it home and checked the fuses and f4 5amp fuse blown in rectifier. Replaced fuse and blew straight away. Have checked all test points on board and seem fine.
Any ideas?
I'm not that technical so short understandable words please!

 

[stevebm1]

probably bad bridge rectifier,easy enough to replace if you can solder

 

[AlanJ]

Unplug J1 & J3 from the rectifier board, try again - does it still blow the fuse? if it does most likely the bridge rectifier (or could be a short in the cabinet on the coin door relay or the knocker relay)

If it doesnt blow, power off then plug J3 back in and try again - this is the power to the backbox. the F4 is 43v, and is used in the backbox to enable the MPU to boot and to provide power to the flipper enable replay on the solenoid driver board, so if it blows again, it could be one of those (but unlikely).

if it doesnt blow, then it's most likely a short on one of the coils on the playfield. There are quite a few, so look for loose wires first!

 

[Paulf]

Cheers both, did a quick check taking off the J1 & J3 and still blew so Bridge rectifier next

 

[AlanJ]

I’d check the knocker and coin door coil as well. I’ve come across a few shorted knockers. You can desolder one wire from each coil. If fuse still blows then it’s the bridge rectifier

 

[Judderman]

I’ve come across a few shorted knockers.

Oo-err missus!